This application claims the priority of German application 197 23 518.2, filed Jun. 5, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a motor vehicle with a rear-mounted air guide device composed of a rear spoiler provided on a rear-mounted hood and a rear airfoil connected therewith.
DE-GM 88 01 032 describes an air guide with a rear airfoil, a rear spoiler, and a hood assembled to form a prefabricated unit. The rear airfoil, which is fixed and located at the top, is connected so that a narrow flow channel is formed with respect to the rear spoiler located beneath.
This known arrangement has the disadvantage that the rear airfoil assumes its operating position even at low road speeds, at which it is not required for producing a downforce on the rear axle. There is also the danger that the air guide device, with its rear airfoil projecting relatively far upward, will be damaged by the washing brushes when passing through an automatic car wash.
An object of the present invention is to provide an improved rear-mounted air guide device with a rear spoiler and a rear airfoil such that the rear airfoil is deployed only when it is necessary to produce the necessary downforce and no damage to the air guide device occurs when going through an automatic car wash.
This object has been achieved according to the present invention by providing that the rear airfoil can be moved by a drive device from a retracted resting position into an extended operating position and vice-versa, with the rear airfoil in resting position being largely lowered into a groove-shaped receptacle provided on the top of rear spoiler.
The primary advantages achieved with the invention include the fact that, as a result of its movable configuration, the rear airfoil assumes a retracted resting position at relatively low road speeds, in which it cannot be recognized as a rear airfoil. Only at higher road speeds at which a higher downforce on the rear axle is required is the rear airfoil moved into its deployed operating position by a motor drive device.
The drive device comprises a central drive motor, two flexible drive shafts, and two telescoping extenders that support the rear airfoil. Each telescopic extender has at least one outer tube held in place on the rear spoiler and an inner tube connected with the rear airfoil. The inner tube is in an operating connection through a spindle drive with the outer tube.
In the retracted resting position of the rear airfoil, the top of the rear airfoil forms the area exposed to the flow over the rear. With the rear airfoil retracted, the danger is reduced that the brushes of the car wash will become jammed in the air guide device as it passes through an automatic car wash, thereby damaging the air guide device.
According to a first embodiment of the telescopic extender of the present invention, the outer tube is fixed and the inner tube connected with the rear airfoil executes a linear displacement movement. The drive device engages the lower edge of the outer tube. The two end positions of the inner tube are controlled by microswitches with endposition recognition.
A second embodiment of the telescopic extender provides a rotary movement of the outer tube. The drive device engages in the vicinity of an upper mount, with the drive shaft driving a worm wheel of the outer tube through a worm shaft. This version of the telescopic extender requires less space vertically.
The worm gear transmission produces a better torque conversion and the torque is produced where it is required. The drive shafts can be made simpler and thinner in cross section. The rotary movement of the outer tube and the linear displacement movement of the inner tube avoids the so-called slip-stick effect between the two tubes, which occurs with simple sliding guides.
Two reed contacts are provided for detecting the end positions, these contacts being mounted outside the outer tube. These reed contacts are actuated with zero contact by a permanent magnet mounted on the inner tube. Because the inner tube, in contrast to the outer tube, does not move, exact switching of the reed contact in the end position is always guaranteed with this arrangement, so that a control connected with the reed contacts can reliably move the telescopic extender.
In a further improvement, the reed contacts are soldered together with a plug on a board which simultaneously forms the electrical connection between the plug and the reed contacts. The board is held in a cavity in the holder so that as to be protected against corrosion. By mounting the reed contacts on the board, the reed contacts are simultaneously held in position and connected electrically with the plug, thereby eliminating separate installation.